On 1/22/2026 6:45 PM, Yeongjin Gil wrote:
When overwriting already allocated blocks, f2fs_iomap_begin() calls
f2fs_overwrite_io() to check block mappings. However,
f2fs_overwrite_io() iterates through all mapped blocks in the range,
which can be inefficient for fragmented files with large I/O requests.
This patch optimizes f2fs_overwrite_io() by adding a 'check_first'
parameter and introducing __f2fs_overwrite_io() helper. When called from
f2fs_iomap_begin(), we only check the first mapping to determine if the
range is already allocated, which is sufficient for setting
map.m_may_create.
This optimization significantly reduces the number of f2fs_map_blocks()
calls in f2fs_overwrite_io() when called from f2fs_iomap_begin(),
especially for fragmented files with large I/O requests.
Cc: [email protected]
Fixes: 351bc761338d ("f2fs: optimize f2fs DIO overwrites")
Reviewed-by: Sungjong Seo <[email protected]>
Reviewed-by: Sunmin Jeong <[email protected]>
Signed-off-by: Yeongjin Gil <[email protected]>
Otherwise, it looks good to me.
Reviewed-by: Chao Yu <[email protected]>
Thanks,
---
fs/f2fs/data.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 2e133a723b99..11c262afad65 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1851,7 +1851,8 @@ int f2fs_map_blocks(struct inode *inode, struct
f2fs_map_blocks *map, int flag)
return err;
}
-bool f2fs_overwrite_io(struct inode *inode, loff_t pos, size_t len)
+static bool __f2fs_overwrite_io(struct inode *inode, loff_t pos, size_t len,
+ bool check_first)
{
struct f2fs_map_blocks map;
block_t last_lblk;
@@ -1873,10 +1874,17 @@ bool f2fs_overwrite_io(struct inode *inode, loff_t pos,
size_t len)
if (err || map.m_len == 0)
return false;
map.m_lblk += map.m_len;
+ if (check_first)
+ break;
}
return true;
}
+bool f2fs_overwrite_io(struct inode *inode, loff_t pos, size_t len)
+{
+ return __f2fs_overwrite_io(inode, pos, len, false);
+}
+
static int f2fs_xattr_fiemap(struct inode *inode,
struct fiemap_extent_info *fieinfo)
{
@@ -4443,7 +4451,7 @@ static int f2fs_iomap_begin(struct inode *inode, loff_t
offset, loff_t length,
* f2fs_map_lock and f2fs_balance_fs are not necessary.
*/
if ((flags & IOMAP_WRITE) &&
- !f2fs_overwrite_io(inode, offset, length))
+ !__f2fs_overwrite_io(inode, offset, length, true))
map.m_may_create = true;
err = f2fs_map_blocks(inode, &map, F2FS_GET_BLOCK_DIO);
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